Under Cold Skin
by Trollala.X
Summary: It was all machine underneath. There was no beating heart, no blood flowing through her veins. She only had half a brain, the rest was the system that controlled her mechanical body. And no matter what she did, her skin was always so cold. "How are you so warm?" NaLu. Robot AU. Rated T.
1. Wake Up Call

**AHHHH, a new story! Ok, so this is based off the drawing Hiro Mashima posted on his twitter a while ago. Hope you enjoy!**

 **Disclaimer: Fairy Tail belongs to Hiro Mashima.**

OoOoO

When she woke, she heard voices all around her, speaking to each other in hushed voices. They became clearer as seconds passed, and they no longer sounded like whispers.

They were loud, too loud. She adjusted her hearing, almost on instinct. She could feel things move inside her, scraping against each other as her ears adapted to her environment.

She concentrated on something else because she knew there was more of her than only her ears. Commands travelled through her body in sonic speed, and she felt her fingers twitch.

She heard gasps, then scratches and tapping. The voices became louder, and again she had to fix up her hearing.

"I think it's working."

"Extraordinary," something whispered.

Confusion.

What was extraordinary? What was working? Nothing made absolute sense.

Information, so much information filled her head. Pictures, articles, and videos flashed through her, looking for an answer for her questions. There were so many answers, so many different things that worked and were considered extraordinary.

Nothing matched up. She couldn't choose.

Her insides tightened, causing great discomfort. She couldn't compute.

There was no reliable information. Her questions were too broad.

Something touched her, sending shocks through her body, and before she could do anything about it, her eyes shot open and the arm that was touched grabbed the nearest thing.

There was a bright light right in her face, but she was not bothered. What she had grabbed tried to escape her grip, but her fingers tightened in response.

She could feel something…pleasant.

She wanted to run her hands over it many times, over and over again. Her eyes moved to the side as far as she could, her eye muscles straining to try to get a better look.

A red grid appeared before her, scanning whatever was before her. Large amounts of data went through her mind, searching for an answer.

"Human," she said in a monotone voice. It sounded strange to her. It sounded…different than the whispers from the other humans.

The human before her gasped, "You really do work," and the other humans around her ran to different parts of the room she was in, mumbling to themselves, but she heard them all clearly.

Blinking, she let go of the human and slowly sat up. She could look around the room more easily in this position. The room was white all around, and machines surrounded her, small lights blinking every few seconds.

She looked down at herself, analyzing her body.

Her right hand, the one she had used to grab the human that was still standing next to her, was made up of a combination of metal and flesh. They merged together to form one whole, functioning hand.

She slowly lifted up her left hand, eyes narrowing when she saw that it was only metal. She clenched and unclenched her fists, satisfied that they worked perfectly. Glancing at the human, she saw a purple spot forming on his wrist.

"You are hurt, human," she stated, fascinated by the way the injured area was imprinted by her fingers. "I did that to you."

"You did," he breathed, rubbing his wrist as she continued to stare at it in awe and curiosity.

"Why is that?" she asked, clenching her right hand again, "My grip on you was nothing compared to how hard I can actually squeeze something."

She looked down again and saw how her right leg was entirely made of flesh, yet fifty percent of her left leg was cold metal that matched her skin color. Going up, her abdomen was covered with her original skin, but she knew inside was all machinery.

"You are incredible," she heard, and she immediately stared straight at the human's eyes, "I never thought this could happen. So many tests, but no results."

She tilted her head. "Yet here I am," she stated, shifting her body to the edge of the table she was on. It felt cold underneath her right leg and hand.

The rest of her was numb, feeling nothing as it slid against the smooth surface.

"Yes, here you are."

She placed a bare foot on the clean floor, testing the feel of the surface. Her other metal foot placed itself next to it, allowing her to stand up with ease. Her right leg felt wobbly from the weight, but she would get used to it.

Another human came up to her, wearing the same white coat the person behind her wore. Something was in her hand, and when the human was right in front of her, she handed her what the data had told her was a mirror.

This was an object that humans used to see how they look. Why would they give this to her? She was not a human.

"I do not see the reason as to why I must look at myself. This is an object for humans," she stated, head tilted to the side as she stared at the woman in front of her.

The human laughed, and she couldn't help but save that image in her mind. "It wouldn't hurt to see how you look."

Though she couldn't understand the purpose of looking at herself, she lifted the mirror.

Her face looked human, and brought a hand up to her face to press a finger to her cheek, awed at how the flesh acted the same way as that of a human. She opened her mouth, surprised to see teeth and a tongue, but there was no hole at the back that indicated the pipes where food and air should go.

Closing her mouth, she glanced at her nose. It was small, nothing abnormal. Her eyes, however, were large. They were almost captivating with the way she stared so intensely at herself.

Her irises were of a golden, honey color. She saw little wires on the surface of her irises, faintly glowing blue as she took in the image. Her pupil had contracted from the bright lights of the room, but she couldn't understand why.

She was not like the rest of the humans. Bright lights did not bother her.

She stretched out her mechanical arm, moving her head to see what was supposed to be golden hair picked up in a high ponytail with a metal bow.

" _You look beautiful, Lucy."_

" _Thanks mom, but I'm not feeling it right now."_

She dropped the mirror.

This was not data at all. Her system was freaking out as something unknown planted itself in it.

"What's wrong?"

She felt her eyes go in and out of focus for a few seconds.

"I am Lucy," she said, almost as if asking, voice going static as she said the name. The man from before moved to her side, his black hair slightly messed up from what her data told her was lack of sleep.

"That is correct," he smiled at her, the woman behind him picking up the shattered mirror. "And I am Zeref, your creator."

"Creator?" she asked, confused as to why and how he was her creator.

The other humans in the room stopped doing what they were doing before, staring at her.

"Yes, I created you to be the perfect killing machine," his smile widened, red eyes staring right at her. "I created you to win the war."

Conversations from when she was unconscious played in her mind.

" _But she's one of them!"_

" _Shut! It is an opportunity to win the war."_

" _But all our other test subjects had failed."_

" _I have faith in her. She's a fighter. I'm sure she won't fail on us."_

" _But her memories!"_

" _I'll erase them all. Do not fret."_

 _There was some scraping of metal against metal._

" _Now, give me the scalpel. It's time to work."_

"I was human once," she stated, staring at the floor as she let the information get put away.

"I saved you from death," said Zeref, his hand coming up to grab her chin. Her forcefully moved her head so that she could stare at him.

Her eyes narrowed, brows furrowed as a sensation of something bad rose up inside of her.

She could not describe such feelings.

"Yet you want me to bring death to other beings," she coldly said, lips pulled into a frown.

Zeref's eyes grew cold, releasing her from his hold.

"Shut her down," he commanded, waving a hand in her direction. "We still have some work to do."

Before she could dwell in what she was feeling, her system shut down, causing the machinery to stop moving as she fell to the floor.

The last thing she saw were black boots in front of her as her eyes closed to see only darkness.

OoOoO

"Where do you think you're going?"

Natsu stopped in his tracks as he cursed his damn luck. He slowly turned around, a nervous grin on his face as he scratched his head. His cat had stopped a few feet in front of him, but only sat on the floor and yawned.

Damn cat.

"Nothin'," he responded, voice a bit shaky as the redhead before him arched an eyebrow at his strange behavior.

Placing a hand on her hip, she asked almost rhetorically, "You do know that we are not to leave the base after sundown, right?"

Eyes moving to stare at the side, Natsu sighed as he realized that he was not going to be able to get out tonight.

"Yeah yeah," he sighed, walking back towards Erza, letting out a pathetic whimper when she gave him a glare as a warning.

"Next time I catch you trying to sneak out, there _will_ be consequences."

"Aye!" he squeaked before shooting off to his room, his cat running behind him. Once he reached it, he quickly opened the door that had a "DO NOT DISTURB!" sign and shut it hard after letting the feline in.

Letting his backpack fall to the floor, Natsu walked to his bed and fell face first into the cushion. Something pressed onto his face, and the pink haired man chuckled as he felt small feet walk on him.

"Enjoy walking on me, Happy?" he asked, slowly turning around so that the cat could get off him without getting squished.

Happy meowed, rubbing his head on Natsu's leg as he happily purred.

Lying down, the man let out a loud sigh, staring up at the ceiling.

This whole war was getting on his nerves. He couldn't get out of the base without someone with him at all times, he couldn't even sit by one of the large windows that had in their base.

Apparently the enemy could shoot you through the windows, but he didn't care. He strived for adventure. He wanted something different than just sitting around all day and planning what the next moves were going to be.

And it didn't help that their enemies had become very quiet for the past few months. Erza said they were planning to do something big, but Natsu secretly hoped that they were thinking about giving up.

But knowing Tartaros, they won't back down without a fight.

Reaching over Happy, who was curled into a furry ball by his side, Natsu turned off the lamp by the bed. Shifting himself, the man laid on his side and closed his eyes.

Before sleep took over, he could have sworn he heard a voice whisper in his ear in a pleading voice.

" _Help me."_

OoOoO

 **Ok, so I'm done with this chapter! I really hope you liked it. I'll try to be consistent with the chapters, but I have to update my other story, so it might take a while. I luckily have break, but I can't promise anything. So ya.**

 **Anyway, I would really appreciate if you left a review! I'm curious to know what you all think.**

 **Bye! :)**


	2. I Will Find You

**Disclaimer: Hiro Mashima is the rightful owner of Fairy Tail, not me. :'(**

 **Sorry for any mistakes! Enjoy!**

* * *

"Why do you hurt me?"

Electric shocks ran up her body in waves, heating up her metallic arm and leg while causing her muscles to tense so much from the electricity that it hurt. Her limbs were strapped down in case she spasmed too much, but her body had been shut down for the past few hours, preventing her from moving at all.

"We are helping you improve," said Zeref simply, looking down into her eyes from where he stood beside her before moving to grab something. The table was cold against her skin.

It was unpleasant.

The black haired man patiently tapped specific places on her head, smiling when it opened up to reveal her brain, but only half of it remained while the other half was an intricate system of wheels and wires, glowing when another shock went through her.

Her vision blurred and a warning appeared before her.

" _Secondary core breached_ ," had escaped her lips almost immediately. The warning flashed red in big, bold letters and her right hand violently twitched as Zeref connected a few wires to her system.

Another shock was sent through her body, this time a little while longer.

An irresistible urge to just choke and break went through her mind. A part of her programming told her not to act on such an impulse, but the other half was telling her body to protect one of its main systems.

Her mechanical arm immediately rose up, bending the metal restraints that had confined her whole arm to the table. Before her fingers could even graze his skin, she stopped. Her arm locked itself in position, trembling as she tried to fight her programming, but commands ruled over and forced her to slowly lower her arm to rest on the cold metal table again, allowing more shocks to run through her.

The other humans spoke to each other in exasperation, almost as if they were tired of dealing with something that just wouldn't act according to planned. They tapped their pens against their little boards as they tried to think of different things to make her improve.

She knew what they were planning to do to her.

She _knew_.

She had tapped into the lab's computer system, collecting all the data they had. She was connected to the whole system, allowing her access to large amounts of information. But she knew that she had easily broken into the computers because they didn't see any harm.

She wasn't going to be able to do anything about it. Their hold on her was increasing, limiting her defenses when it came to harming a member of Tartaros.

What they commanded, she did. She was their puppet pulled by the strings tangled around their fingers.

Somebody laughed, and her data told her that the laugh matched to that of Zeref's. It was laced with hidden malice, like a promise of more pain.

"You never learn, do you?" he asked, smile widening when she didn't respond. He continued to poke at her system, inserting new programs and commands, helping her "improve".

"It is only a reflex to hurt whatever it is that attempts to harm my vitals," she replied, staring at the light above her, eyes focused on the bulb with ease without tearing her eyes away.

"Vitals?" Zeref laughed, head thrown back and shoulders shaking slightly before he composed himself in a matter of milliseconds and continued on with what he was doing. "Even if the original side of your brain is damaged, you will still be able to function."

He stepped back and moved the light away, looming over her to shadow her face. "That half brain of yours is what keeps you from being more machine than human. Be grateful I left it there."

Going back to his original standing position, he disconnected the wires he had plugged to her head and pressed the same spots he had touched before. He pulled his fingers away as her head closed by itself, clicking when her system was secured.

" _Secondary core secure._ "

The warning disappeared from before her eyes and her vision cleared once again, allowing the room to seem less blurred. She felt a hand on her cheek, thumb slowly massaging small circles on her skin.

 _A hand pressed on her forehead, but she was too delirious to even look who it was._

" _You definitely have a fever."_

 _The cold hand moved down to her cheek, a smooth thumb drawing circles on her warm and sweaty face._

" _Don't worry, I'll make sure you get better soon."_

"Stop."

Zeref stilled, waiting for her to react violently like the other times. Another shock went through her body, and she could feel the electricity run through her legs, past her abdomen, up her neck, and into her head.

His hand pulled away when he was zapped, cradling his hand with the other, still staring at her face, "What goes through that mind of yours?"

Slowly, ever so slowly, her eyes moved to look directly at him. Her mind tried to come up with an answer for his question, but she couldn't think of anything. And so, she gave him what seemed to be the most obvious answer for both of them.

"Data," she responded, and she watched how Zeref's look of wonderment fell into a straight poker face. She worried that she gave him the wrong answer so she tried even harder to search for a better one.

What stopped her was when Zeref started laughing, clutching his stomach, and from what she analyzed, his abdomen muscles were very tight, most likely causing a slight cramp.

Explained why he had an arm pressing into it.

"Why do you laugh?" she asked, mesmerized by the way he smiled with small droplets of tears on the corners of his eyes, teeth flashing as continued on what he was doing.

When his laughter started to die down, her data told her that he had been laughing for around half a minute.

She was…confused.

From her earlier observations of the other humans, they would laugh for only a few seconds after somebody said something or something happened. Never had she seen a human laugh for so long.

Wiping a tear, Zeref smiled at Lucy, "You really are incredible."

"Do you find what I said," she thought of what she was going to say next, trying to find the right word that fit what she wanted to say, "…amusing?"

Chuckling, the dark haired male shook his head in what seemed to be in awe, "You are curious about everything, now aren't you?"

Lucy slowly sat up and turned to let her legs hang from the metal table, shocks still going through her body, but they were much less powerful. The waves of electricity almost soothed her, a source of heat that warmed her body.

"It is who I am," the blonde stated as the voice of a young girl played in her mind, asking questions to someone.

Always asking questions.

Tilting her head, Lucy tried to remember about her previous life, before she had nearly died. All she got was the image of a woman that looked just like her, but more human…older.

"But who am I really?"

Her body was starting to shut down as the other humans pressed certain buttons on the machine that was connected to her limbs with black wires. Her muscles stopped working and her back couldn't support her weight so she collapsed against the table rather hard.

She felt a twinge of pain at the back of her head, but it was only a slight sting that lasted less than a second. Lucy tried to open her mouth to ask what was happening, but she had no control over her body whatsoever.

Why were they doing this to her? She thought they finished fixing her. What more was there to improve of her.

Another machine was pushed to the side of the table as other people grabbed her heavy legs and heaved them over the table. A loud clang echoed through the room as metal met metal, but she didn't feel a thing. She knew that they were detaching a part of her mechanical leg, but her system did not inform her that such a thing was happening.

Her eyes started to close, and she tried with all her might to keep them open as long as she could, but how could she control her own body when other people could do it for her with only a simple press of a button.

Before they closed completely and before her hearing also stopped functioning, she heard Zeref whisper something to her, and even though he was a good distance away from her, she heard him clearly.

"You are Lucy. That is all you need to know."

And once again, the room went dark and her sense of hearing stopped working, and all she could do was wait in her lonely, quiet world until they turned her on again.

* * *

"I'm telling you, their base could be located here!"

Natsu tried to keep his cool (stupid Gray), but it was nearly impossible to when his friends weren't even trying to think about the possibilities.

Erza sighed, obviously irritated with his behavior, but calmly responded, "That is not possible. That is a highly radioactive area, and any person that decides to step into a place like that is looking for a death wish."

Groaning, the male ran a hand through his pink hair, scratching the scalp in an effort to come up with a logical answer.

Next to Erza sat a blue haired woman around the age of 20, furiously scribbling notes on a parchment as if she depended on it. Her red glasses occasionally slipped a few centimeters down her nose before she pushed them back up again. After a few seconds, the woman dropped her pen and looked straight at Erza.

"It is possible," she declared, softly rubbing her chin in thought as she stared at the ceiling, "Tartaros is very advanced in technology, and as you may know, they're not exactly completely human."

Standing up from her chair, the blunette's orange dress swayed with each step she took as she walked around the table to stand next to the red head.

"They may seem just like us, but their DNA is structured differently from ours," again, her glasses slipped just a little, but she corrected them with a gentle push, "They did invade us, after all."

Natsu internally cheered when he saw Erza contemplate Levy's answer. The male was never the smartest cookie, so he was relieved that someone smart had decided to take his side.

"Okay," the red head slowly said, turning back to the map of the region, "I can't deny that they are not affected by the same things we are, but what makes you think I would send some of our people to a highly dangerous area?"

Erza turned around to lean on the desk, arms crossed as she closed her eyes, "We're not even sure if they are actually there."

He knew that it was risky entering such an area, but he had to trust that voice. They had been searching for months now, but there had not even been a clue that could lead them to their enemy.

The last time they were seen was right before the incident where he had been captured by their enemy. His friends found him the next day dumped on the ground near where he was captured originally.

Natsu had no memory of what happened when he was in their clutches, but he had come out untouched. No matter how much he tried, the only thing he could remember was something golden that flashed in the corner of his eye before everything went black again.

Their devices were limited, they weren't as advanced as that of Tartaros, so tracking them was even harder.

"Just a question," he heard and his head snapped back up from where he was staring at the ground, "What made you come to such a conclusion?"

Natsu panicked as he tried to come up with a logical response. He couldn't exactly tell the red head that he only listened to the voice that told him their enemy's location out of the blue after only talking to it for a few nights.

"Well," he started out, sweating bullets when Erza opened her eyes to stare directly at his face, and he knew that she could tell he was nervous. "I figured that since we've checked every other place other than that region with no results, I thought that the only other place they could be was there."

He saw Erza's eyes narrow when he grinned, but she closed them again and shook her head, turning back around and glanced at the map.

Natsu saw Levy send him a smile and a wink behind Erza, and he couldn't help but grin back in appreciation.

"I guess we could send a small robot to check out the area before sending any of our people to that zone," she concluded, nodding as she approved of her own idea, brows untightening as she relaxed from her tense state.

Looking back up, the red head smiled at Natsu, eyes glinting in amusement, "You're a horrible liar, but I know you don't lie unless it's for a good reason."

Grabbing the map, Erza rolled it up to put it away underneath the desk, the paper crinkling loudly from age. After placing it in a cabinet under the surface of the desk, the red head walked around the table with Levy following behind her.

Erza reached out and pat Natsu's head, ruffling his hair like a sister would do to a younger brother. With that, they all left the room to eat breakfast with the rest of their friends.

* * *

She tested out her new weapons that were installed into her while she was shut down.

Commands ran through her body and a long blade replaced her left hand, glinting in the bright lights of the room. It curved like the blade of a scythe with golden waves decorated on its side. Bringing it closer to her face, she inspected the sharpness of the blade, satisfied that it wasn't the least bit dull.

"That blade will never dull as long as you put it away after every use," the dark haired man said, circling around her to see her reaction towards the new additions that he made. "Inside your arm are tiny sharpeners that ensure your blade is fit for slicing victims with little resistance."

"It is made of the same material as the rest of my body," she stated, turning her arm to look at the other side, "Steel."

"That is right," Zeref nodded, his hands grasped behind him as he stopped beside her. "Want to test it out?"

With that, a dummy came out from under the floor and slowly rose up. Standing up, Lucy walked away from the table, letting her eyes calculate the distance from her and her "opponent".

A split second later, she was standing across the room, eyes hooded as she stared at the ground with the scythe no longer out, instead replaced by her hand.

The whole room stood quietly as the upper half of the dummy slowly fell to the floor face first. Lucy clenched her fist as an irresistible urge to kill entered her system, invading her brain as her programming tried to take over.

"Now," she heard behind her, and she didn't even need to guess who it was, "ready to try out the other ones?"

 _If you don't find me soon, I'll come find you._

Her hip opened up to reveal a whip, and without thinking, she grabbed it and attacked the next dummy that came up.

* * *

 **Auuugghhh, this story is taking a totally different route that what I expected it to be. I don't know what to do with my brain sometimes. Anyway, a slightly longer chapter this time, so yay! Thank you so much for everybody who reviewed, and I'm sorry I won't be able to answer you for last chapter, but I will hopefully for this chapter! You can't imagine how frustrating it is to have my mom use the computer right when I get this inspiration to write. It's annoying, but whatever.**

 **Anway, thank you so much for reading, and reviews are always much appreciated! It wouldn't hurt to see what you guys think about this chapter. I'll try to explain more about what's happening next chapter, and hopefully Natsu and Lucy meeeeeting.**

 **Bye! :)**


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